As is set forth in my aforesaid patent, the torque on the drive shaft of an automotive vehicle can be determined through the measurement of the resistance of an included strain gauge, yet without the need for a power supplyxe2x80x94such as a battery, on the rotating shaft itself. More specifically, the apparatus of that invention described the transmitting of electrical power from a first place A to a second place B in the direction A to B, for the purpose of powering electrical and/or mechanical equipment used in the measurement of, or operation of, equipment mounted at the second place B. Information obtained through the apparatus of that invention was then generated and transmitted back in the direction B to A, without any mechanical connection whatsoeverxe2x80x94while, at the same time, allowing a relative movement of A and B in various coordinates. With the invention set forth, mechanical and electrical functions were then allowed to be performed on B, with information to be obtained on B, then being transmitted back to A, without any source of power on B.
In a preferred embodiment of the invention there described, a first means was included for transmitting electrical power from a first location towards a second location; second means was located at the second location, responsive to the electrical power received from the first means, for the purpose of operating a utilization apparatus; third means was then coupled to the utilization apparatus for generating a signal indicative of its performance, and for transmitting that signal back to the first means via the second means. To carry that out, the first means was stationary in operation, while the second means was mechanically rotational in operation, as where the first means included a fixed electrical coil while the second means included a rotating electrical coilxe2x80x94and in the automobile, truck and motor vehicle environment then in question for measuring horsepower, the second means included an electrical coil on a rotating mechanical shaft.
In the preferred embodiment of the invention there described, the first means further included an electrical power oscillator of given frequency, with the fixed electrical coil and the rotating electrical coil both being tuned to resonate at the frequency of the oscillator. In particular, the fixed electrical coil and the rotating electrical coil were magnetically coupled to constitute a critically coupled transformer tuned to the frequency of the electrical power oscillator. With very small coupling coefficients between the coils of the critically-coupled transformer, an almost 100% efficiency of operation was attained, with the result being that a substantial change in primary current (reflecting the signalling), made possible a remote locating of the fixed apparatusxe2x80x94all possible with a single pair of wires for the connection to the transformer.
Where a strain gauge was mounted on the rotating mechanical shaft, and where the third means generated a signal indicative of the strain gauge at any given instant of time, a digital signal was generated indicative of the resistance of the strain gauge, as utilized in determining the horsepower delivered to the wheels of the vehicle. As there described, such operation was accomplished with the second means being devoid of any source of operating power, and with an absence of mechanical interconnection between the first means and the second means.
Simply stated, in my previous, U.S. Pat. No. 5,801,644 patent, the transmission of both power to the rotating part, and the torque information from the rotating part, was accomplished by means of a tuned transformer consisting of two circular windings around the shaft, coaxial with one another, and closely spaced with no mechanical contact. One winding rotated with the shaft, while the other winding was non-rotating, and was connected by a cable to the fixed part of the vehicle. In accomplishing this so that the torque on the drive shaft (or axle) of an automobile could be measured, the non-rotating winding was held in proper relationship with the rotating winding, and by an arrangement which included a ball bearing mounted on the shaft.
This invention represents a variation in the apparatus described in such patent, so as to simplify the manner by which the apparatus of this earlier invention could be used. As will be appreciated by those skilled in the art, winding the transformers, making the necessary connections to other circuitry, and installing a bearing could be somewhat impractical to do while the shaft is in its normal position on the car. Experience has shown, in fact, that it is a simpler procedure if the shaft were first removed from the vehicle and disassembled, before the transformer windings on the shaft and the bearing were installed. Such removal operation, and later remounting of the shaft, results, however, in an expense of installation to the torque measuring apparatus, which it would be desirable to avoid. As will be understood, this led to the development of the articulated transformer of the present inventionxe2x80x94the importance of which allows the installation to be accomplished in just a few hours, at a xe2x80x9cspeed shopxe2x80x9d, in much the same way as if a servicing were done in an automotive repair shop. With the invention at hand, the result follows that one need not have to take off the wheel or the boots, to take the axle completely apart, let alone having to purchase a bearing for the installation, which typically costs some $50.00 and more.
As will be seen from the description that follows, the present invention employs an articulated transformer for the coupling, which does not require access to the ends of the drive shaft (or axle) for installationxe2x80x94and can be installed with the shaft in its normal position on the automobile, whether the ends of the shaft are accessible or not. In the preferred embodiments described, the windings of the transformer do not completely encircle the shaft, but leave a small gap so that the mounting structure can be opened, and the winding slipped over the shaft, before being closed again to form the complete transformer. Although the net inductance is reduced, the proximity of the coils is retained sufficiently close to obtain a high coupling coefficient, with the spacing being only so much as to allow the transformer to slip around the axle. In fact, with an axle of some 1xe2x80x3 or so in diameter for a front wheel drive automobile, or for a rear wheel drive automobile with independent suspension, the articulated transformer of the invention will be appreciated to fit right over the axle. Measurements taken, and in accordance with the formulations set forth below, indicate that the magnetic field produced with the gap in the transformer is almost identical to the field that would exist if the gap were not present. At the same time, with this articulated transformer, the need for any bearing to maintain the proper relationship between the windings becomes unnecessary, leading, in part, to the simplification of installation and reduction in expense desired.